The use of hydraulic cylinders for lifting heavy loads is well known. A common problem in the use of hydraulic cylinders in dirty or underwater environments is contaminants entering into the hydraulic system and causing problems with the hydraulic pumps. Contaminants such as mud, dirt, marine growth, and mineral deposits build up on the cylinder rod and are dragged through the seals of the cylinder barrel. One of the most challenging contaminants are mineral deposits because they are microscopic particles diluted into water. As water flows around the cylinder rod minerals such as calcium carbonate attach to the cylinder rod.
There are many solutions for protecting a hydraulic cylinder shaft in above water applications, but most will not work in an underwater application for various reasons that will be described. The most common cylinder rod protection is a boot that prevents contaminants from contacting the rod of a cylinder. These can be seen in use on motorcycle shock absorbers, heavy machinery and more. The main problem with using a standard boot on an underwater cylinder is the change in volume inside the cylinder boot when the cylinder expands and contracts. Standard cylinder boots allow air to free flow in and out of the boot such as in U.S. Pat. No. 6,932,356 to Gloaguen. If the standard cylinder boot is used underwater the boot will implode while the cylinder extends because the cylinder boot cannot suck in water at same rate it can suck air in. When the cylinder retracts the cylinder boot will balloon because the cylinder boot cannot push water out as fast as it can push air out. A simple solution to allowing water to flow in and out of the cylinder boot would be to add a large vent hole. The cylinder boot with a large vent hole would work to keep large contaminants off of the cylinder rod, but because the hole in the cylinder boot allows water to free flow in and out of the cylinder boot unlimited minerals can float into the cylinder boot and attach to the cylinder rod still leaving a contamination problem.
Another common device used to prevent contamination entering into a hydraulic cylinder is an internal cylinder scrapper. U.S. Pat. No. 4,577,363 to Wyse, U.S. Pat. No. 4,461,486 to Tregonning and U.S. Pat. No. 6,047,970 to Friend are examples of cylinder scrapers. Internal cylinder scrappers are knife edged rings, made from stainless steel or bronze, that are fixed into a cylinder head above the cylinder seals. Internal cylinder scrappers do a good job of removing large marine growth like barnacles, but they allow small particles like mineral deposits or marine growth residue to pass through into the cylinder.
Accordingly, there is a need in the art for a cylinder contamination protection system suitable for underwater use that protects a cylinder from one or both of large contaminants such as mud, dirt and marine growth, and small contaminants such as mineral deposits and marine growth residues.